After some research maybe the mail should have equal (and other characters) changed to =3D(since it's quoted-printable) , but I can't figure out why characters like åäö don't work.
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Tim BrunsmoMay 11 '12 at 0:33

2 Answers
2

It was not a problem on my side, it was SendGrid.
Mails sent through SendGrid with characters like "åäö" does not work in mail clients like yahoo/outlook/MacMail.

After a few hours of support with an employee at SendGrid the problem still persists.
They say that the problem is in my setup.
I've now switched to mailgun with exactly the same setup and it works great.